1. Field of the Invention
This invention relates to chain extenders for polyester elastomers, and, more particularly, to a one-pot, two-step process for preparing 2,3-bis(hydroxymethyl) bicyclo [2,2,1] heptane (BHMBCH) in a non-toxic solvent for the preparation of polyester therewith.
2. Description of the Prior Art
BHMBCH has been described in the literature. See Birch et al., J. of Org. Chem. 21, 970-974 (1956). The Birch synthesis involved three separate steps, namely, (1) a Diels-Alder condensation of cyclopentadiene and maleic anhydride to form an unsaturated anhydride; (2) reduction of the anhydride with lithium aluminum hydride to produce an unsaturated diol; and (3) hydrogenation over a palladium catalyst to provide the saturated diol. However, in the process, a considerable quantity of undesirable by-products were obtained during step (2), and, accordingly, four crystallizations of the crude unsaturated diol were required before the hydrogenation step (3) could be carried out effectively.
French Patent No. 857,937 described the preparation and isolation of the unsaturated diol intermediate only. The process comprised reaction between cyclopentadiene and 1,4-butenediol in dioxane solvent. However, dioxane is extremely toxic and difficult to remove completely from the reaction product.
U.S. Pat. No. 3,492,330 disclosed reactions of bridged-ring olefins, including the unsaturated diol with functional alkanes. The patentee said the unsaturated diol could be prepared from cyclopentadiene and 1,4-butenediol by a classical Diels-Alder reaction.
In summary, the prior art does not provide a commercial process for the preparation of the desired saturated diols, particularly in a one-pot, two-step process, and a non-toxic solvent which can be used for both the condensation and hydrogenation steps.
Accordingly, it is an object of the present invention to provide a new and improved process for preparing 2,3-bis(hydroxymethyl) bicyclo [2,2,1] heptane by a one-pot, two-step synthesis in a non-toxic solvent.
Another object of the invention is to provide polyester with 2,3-bis(hydroxymethyl) bicyclo [2,2,1] heptane.
These and other objects and features of the invention will be made apparent from the following more detailed description of the invention.